| 1. |
- Ohlsson, Nicklas, et al.
(författare)
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Quantum computer hardware based on rare-earth-ion-doped inorganic crystals
- 2002
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Ingår i: Optics Communications. - 0030-4018. ; 201:1-3, s. 71-77
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Tidskriftsartikel (refereegranskat)abstract
- We present a scheme for generating multiple, strongly interacting qubits in rare-earth-ion-doped inorganic crystals at cryogenic temperatures. Two ground state hyperfine levels, with hour long lifetimes and ms decoherence times are chosen as qubit states. Controlled logic between the qubits is accomplished using the change in permanent dipole moment induced by an optical transition between the ground and excited state of these ions. The scheme is based on existing material data and established measurement techniques and should therefore be straightforward to realise in practice. The procedure used for creating the qubits can be generalised also to other solid state systems.
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| 2. |
- Samsöe Andersen, Eva, et al.
(författare)
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Improvement of brightness and output power of high-power laser diodes in the visible spectral region
- 2003
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Ingår i: Optics Communications. - 0030-4018. ; 219:1-6, s. 369-375
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on a novel design for a high-brightness quantum-well AlGaInP laser-diode system operating at 635 nm. The spatial coherence of two broad area laser diodes is improved using spatial filtering and optical feedback from a narrow mirror stripe on each laser. To increase power, the outputs from the two systems are passively combined using a polarizing beam splitter. The result is a compact system providing a high-brightness beam. The beam-quality parameter is improved in one direction from M-2 = 12 and M-2 = 16 for the two lasers, to M-2 = 2.1 for the combined beam. The other direction of the beam is left unchanged due to its natural high quality with an M-2 value around 1.5. A procedure for efficient coupling of the two lasers into a small core-diameter optical fiber is given. This capability facilitates a wide range of applications including interstitial medical therapies, where delivery of the treatment light through thin optical fibers is essential. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 3. |
- Beck, M., et al.
(författare)
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A pulse-train laser driven XUV source for picosecond pump-probe experiments in the water window
- 2001
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Ingår i: Optics Communications. - 0030-4018 .- 1873-0310. ; 190:06-jan, s. 317-326
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Tidskriftsartikel (refereegranskat)abstract
- We describe the development of a table top soft X-ray source based on a laser produced plasma. The plasma is produced by a Nd:YLF pulse-train laser which delivers pulse trains of up to 400 pulses each of about 25 ps duration, Number and energy of the micropulses are fully computer controlled adjustable for an optimum interaction with a rotating solid target. Spectral, spatial and temporal characteristics of the X-ray emission from Mylar and copper targets have been studied. A calibrated back-illuminated CCD camera together with a slit grating spectrograph were utilized for the measurement of the absolute soft X-ray photon fluxes. The temporal measurements were performed using a streak camera while the plasma size was measured with a zone plate. An application of the system in a X-ray absorption experiment is shown, The advantages of the system in view of possible optical pump and soft X-ray probe experiments will be discussed.
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| 4. |
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| 5. |
- Friberg, Ari T., et al.
(författare)
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Focal shifts of converging diffracted waves of any state of spatial coherence
- 2001
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Ingår i: Optics Communications. - 0030-4018 .- 1873-0310. ; 196:06-jan, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the focusing of wave fields of any state of coherence by systems with low Fresnel numbers. We study the optical intensity on the axis in the focal region. The dependence of the focal shift and of the maximum on-axis intensity on the state of coherence is examined for some model fields.
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| 6. |
- Grilli, Simonetta, et al.
(författare)
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A Mach-Zehnder interferometric system for measuring the refractive indices of uniaxial crystals
- 2002
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Ingår i: Optics communications. - 0030-4018. ; 202, s. 9-15
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Tidskriftsartikel (refereegranskat)abstract
- We report a new interferometric technique for measuring the ordinary and extraordinary refractive indices of uniaxial crystals. The technique is based on the measurement of the rotation-dependent phase changes of the optical path length in crystal plates. Accurate measurement of the phase shift as a function of the rotation of the sample is achieved by using a fast-Fourier-transform based fringe analysis method for phase retrieval. The principle of the method is discussed and measurements of the ordinary and extraordinary refractive indices of a lithium niobate crystal are reported.
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| 7. |
- Karlsson, G., et al.
(författare)
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Q-switching of an Er-Yb : glass microchip laser using an acousto-optical modulator
- 2003
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Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 217:06-jan, s. 317-324
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Tidskriftsartikel (refereegranskat)abstract
- We present a compact Q-switched Er-Yb:glass microchip laser operating at the wavelength of 1.535 mum using an acousto-optical modulator. A Q-switched peak power of 325 W with a pulse-duration of 38 ns and a pulse-to-pulse jitter of less then 10 ns was achieved. Well-controlled pulses were obtained for repetition rates up to 10 kHz while the maximum pulse energy was 12 muJ. The experimental results are compared with theoretical analysis, which shows how to optimize the laser as well as fundamental limitations.
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| 8. |
- Ostlund, P., et al.
(författare)
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Radiometry and far-zone polarization for partially coherent electromagnetic planar sources
- 2001
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Ingår i: Optics Communications. - 0030-4018 .- 1873-0310. ; 197:03-jan, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Making use of the rigorous vectorial far-field theory the generalized radiance of a stationary electromagnetic planar source is derived and expressions for the radiant intensity and the radiant emittance are introduced in terms of the spatial coherence properties of the source. A method for calculating the degree of polarization of the field in the far zone of an electromagnetic planar source is put forward and two examples demonstrating the technique are worked out.
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| 9. |
- Paakkonen, P., et al.
(författare)
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Partially coherent Gaussian pulses
- 2002
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Ingår i: Optics Communications. - 0030-4018 .- 1873-0310. ; 204:06-jan, s. 53-58
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Tidskriftsartikel (refereegranskat)abstract
- The concept of a plane-wave pulse with a Gaussian spectrum and a Gaussian distribution of correlations between different frequency components is introduced. The temporal coherence properties of such a pulse are related to the spectral coherence properties and equivalence relations between pulses with different spectral and temporal correlation parameters are established.
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| 10. |
- Petermann, Ingemar, et al.
(författare)
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Limitations of the interferometric side diffraction technique for fibre Bragg grating characterization
- 2002
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Ingår i: Optics Communications. - 0030-4018 .- 1873-0310. ; 201:4-6, s. 301-308
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Tidskriftsartikel (refereegranskat)abstract
- We make a quantitative investigation of the interferometric side diffraction technique for characterization of fibre Bragg gratings. As opposed to more commonly used non-interferometric alternatives, this method also allows for determination of the grating's distributed phase. It is shown that for weak gratings the detected power and phase are directly proportional to the amplitude and phase of the refractive index modulation in the fibre. While the phase measurement is only limited by the amount of noise present, the relation between modulation amplitude and detected power becomes non-linear when using small probe beam wavelengths and gratings with a modulation depth Deltan approximate to 10(-3) and above. This behavior is inherent to the side diffraction and thus care has to be taken when performing apodization measurements on very strong gratings. The sensitivity to noise is briefly discussed and using a crude estimate for the noise level. the theory indicates that this method is suitable down to a grating modulation depth of at least Deltan approximate to 10(-5).
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